I ask students to write down what they know about flowers. I give them about 3-4 minutes at most. All I want them to do is activate their thinking and then we will discuss this further. Depending on where they came from, their knowledge level on the plant cycle varies. Then I show them this short video with images of flowering plants:
Today we go on a field trip to the playground. The students task is to find as many example as possible of flowers, plants that sometimes have flowers, or plants that they think might have flowers. They can record their findings with a written description, a diagram, an illustration, or any combination. My students have defunct smartphones that I allow them to use to take photographs, though we than have difficulties with image transfer because the school district won't permit these phones to access wifi. Anyhow, the point of this exploration is for them to think about the plants they see everyday and to reflect more deeply on the purpose of flowers, especially if they have never studied flowering plants before. If your school's area has conifers and other non-flowering species have students record what they see, and their questions, and then this provides a rich topic for discussion that leads into the next lesson on ferns.
At the conclusion of the exploration, students share what they saw, label with names as many of the plant species as possible, and draw a simplified version of the life cycle of a plant using one of the plants they visited today.